Swell control for bucket ladder



March 11, 1969 c. LUDWIG SWELL CONTROL FOR BUCKET LADDER Sheet Filed June 1966 March 11, 1969 c. LUDWIG SWELL CONTROL FOR BUCKET LADDER Filed June l, 1966 March 11, 1969 c. LUDWIG SWELL CONTROL FOR BUCKET LADDER Sheet Filed June l, 1966 1 N VENTOR.

CHQ dh//G United States Patent O 3,432,043 SWELL CONTROL FOR BUCKET LADDER Carl Ludwig, Cleveland, Ohio, assignor to McDowell- Wellman Engineering Company, Cleveland, Ohio, a corporation of Ohio Filed June 1, 1966, Ser. No. 554,499

U.S. Cl. 214--14 Int. Cl. B63b 27/22; B65g 21/16 13 Claims ABSTRACT OF THE DISCLOSURE Generally, the present invention relates to an improved material handling apparatus and more particularly to a novel mounting or suspension system for an excavating means of the type generally used either to excavate earth formations or to reclaim bulk materials from piles or containers such as the holds of barges or ships.

In apparatus of this general type, the excavating means is mounted on a long boom or other means for enabling the apparatus to work a relatively large area. In operation, the excavating means or apparatus of this type is often subjected to substantial and sometimes excessive loads. For example, an inadvertent collision of the excavating means with the work or other object subjects the excavating means to a high impact load as will caving in of relatively loose materials upon the excavating means.

A further and more serious problem is encountered when unloading bulk cargo carriers which rise and fall with harbor swells. A severe harbor swell causes the vessel to suddenly rise several feet exerting a large upward force upon the excavating means which may either damage the excavating means or cause it to punch a hole through the vessels tank top.

The present suspension system minimizes the effects of such loading conditions by mounting the excavating means so that it is free to move both vertically and pendulously relative to the remainder of the apparatus. Such movement is provided by suspending the excavating means from the remainder of the apparatus on a pair of vertically mounted hydraulic cylinders. The cylinders are actuated through an accumulator loaded hydraulic system designed to maintain a substantially constant pressure Within the cylinders and thereby counterbalance the live load of the excavating means to give the excavating means a floating suspension. This arrangement has a cushioning effect in that it substantially eliminates the weight factor of the excavating means thereby permitting it to move easily with the collision forces.

In an unloader designed to operate in the hold of a ship, the excavating means is mounted on a carrier or ladder structure suspended from a boom on a pair of hydraulic cylinders. This gives the ladder and the excavating means a cushioned freedom in the vertical direction which allows the apparatusto follow the tank top rise with the harbor swells and also reduces the collision forces with the tank top when the excavating means is lowered into the hold or when it is positioned for a cleanup pass on the tank top.

Any Ifore and aft forces exerting on the apparatus such as by a cave-in or a collision of the ladder with the hatch coamings are accommodated by differential movement ICC between the two vertical cylinders and ball joint connections between the cylinders and the ladder which give the ladder a fore and aft pendulous motion.

To permit transverse pendulous motion as well as vertical motion, the pivot connection between the ladder and boom includes pivot wheels which roll along vertical anvil plates on the end of the boom as the ladder rises. The vertical cylinders and anvil plates. are kept vertical regardless of the boom angle by an equalizer system of movable parallel elements. A pair of horizontal cylinders extending between the top of the ladder and the boom serve the dual purpose of resisting rotation of the ladder about the pivot wheels under normal operating conditions and functioning to tilt the ladder to any desired angle from the perpendicular to give it a pendulous motion transversely of the hold. The transverse pendulous motion allows the excavating means to reach farther under the hatch coamings thereby reducing the amount of material which must be removed by slower final clean-up methods.

An important object of the present invention is to provide an improved mounting system for an excavating means.

Another important object of the present invention is to provide a mounting system for an excavating means which cushions and minimizes the collision forces exerted on the excavating means.

A still further object of the present invention is to provide a suspension system for a ship unloader which permits the excavating means of the unloader to rise freely with the ship during a harbor swell.

Another important object of the present invention is to provide a suspension system for a ladder suspended excavating means which permits conical pendulous movement of the ladder and excavating means.

Still further objects and advantages of the present invention will become apparent from the following description and drawings, wherein:

FIGURE l is an elevational view of a ship unloader incorporating the present invention;

FIGURE 2 is a side view of the suspension connection between the boom and the ladder;

FIGURE 3 is an end view of the suspension system shown in FIGURE 2;

FIGURE 4 is a cross section of the suspension cylinder and ladder connection; and,

FIGURE 5 is a schematic diagram of the hydraulic system for the suspension cylinders.

The illustrated embodiment shows the suspension system of the present invention incorporated in a dockside unloader for large deep draft bulk cargo vessels. Generally, the unloader includes a structural tower 10` mounted on trucks 14 adapted to move along a dock 11 lengthwise of a Vessel 12 from one hold 13 to another.

The bulk material is scooped from the hold 13 by a bucket leg elevator including a digging or reclaiming wheel 15 rotatably mounted on the lower end of a carrier or ladder 17. The ladder 17 is suspended from a boom 18 extending outwardly from the tower 10 by a suspension system of the present invention and generally indicated by the numeral 30. The wheel 15 deposits the bulk material into an endless bucket chain elevator 20 running through the center portion of the wheel 15 and forming a closed conveyor circuit extending from the bottom to the top of the ladder 17.

At the top of the ladder 17, the material is dumped onto a short first conveyor belt 21 which transfers it to a second conveyor belt 22 extending along the length of the boom 18. The second conveyor 22 transfers the material to a third conveyor belt 23 in the tower 10 from which it is transferred to a suitable material handling apparatus (not shown) on the dock 11.*The digging wheel and bucket leg elevator form no part of the present invention except as described herein and may be constructed according to m-y co-pending application, Ser. No. 524,404, filed Feb. 2, 1966.

In order to shift the digging wheel and the ladder 17 across the ship from one side of the hold to the other, the inner end of the boom is pivotally connected to a pair of shuttle carriages 24 which are moved perpendicular to the length of the vessel by a pair of long shuttling screws 25. The boom 18 is supported at its outer end by hoist cables 16 extending from a hoist 29 over a mast 19 on the tower 10 to the outer end of the boom. The carriage shuttling arrangement and hoist system form no part of the present invention except as described herein and may be constructed according to my co-pending application, Ser. No. 525,209, filed Feb. 4, 1966.

The suspension system 30 suspends the ladder 17 from the boom 18 on a pair of hydraulically actuated suspension or swell cylinders 31 and 32 located on opposite sides of the ladder 17. The upper ends of the swell cylinders 31 and 32 are pivotally connected by pins 35 and 36 to yokes 39 and 40 on the upper ends of a pair of swell cylinder levers 37 and 38 respectively. Each of the swell cylinder levers 37 and 38 is pivotally connected adjacent ils lower end to the outer end of the boom 18 as shown at 42 in FIGURE 2.

The ladder 17 pivots inshore and outshore relative to the tower 10 about a cross shaft 45 upon the respective ends of which are rotatably mounted pivot wheels 47 and 48 which bear against vertical anvil plates 65 and 66 on the lower ends of the swell cylinder levers 37 and 38. Adjacent the pivot wheels 47 and 48 on the cross shaft 45 are a pair of substantially pear-shaped plates 49 and 50 which are pivotally connected at their upper ends by pins 53 and 54 to clevises S7 and 58 on the lower ends 0f piston rods 61 and 62 depending from the swell cylinders 31 and 32 respectively.

Referring to FIGURE 4, wherein the left hand swell cylinder 32 and ladder connection are shown in cross section, the swell cylinder 32 includes a cylindrical body 70 having upper and lower end caps 71 and 72 sealingly secured to the cylinder body 70 by bolted fiange connections 75 and 76 respectively. An axially movable piston 78 is mounted within the cylindrical body 70 and provided with a piston rod 62 extending to the exterior of the swell cylinder 32 through a packing gland 79 in the lower end cap 72. The upper end cap 71 is provided with exhaust ports 80 through which uid is exhausted from the upper portion of the swell cylinder 32 as the piston 78 moves upwardly in the cylinder body 70. Hydraulic fiuid is admitted into the cylinder body 70 beneath the piston 78 through an inlet port 82 in the lower end cap 72.

The lower end of the piston rod 62 is threaded to the clevis 58 at 63 and the clevis 58 is rotatably connected to the pear-shaped plate 50 by the pin 54 and bushing 55. To accommodate fore and aft tilting of the ladder, the plate 50 is pivotally connected to a reduced end portion 46 on the cross shaft 45 by a ball and socket joint 83. The pivot wheel 48, is rotatably mounted on the shaft 45 next to the plate 50 in opposing relationship to the anvil plate 66.

Referring to FIGURE 1, an equalizer system is provided on the boom 18 to keep the anvil plates 65 and 66 vertical regardless of the angle of the boom 18. It is to be understood that each of the anvil plates 65 and 66 has an identical equalizer system and for the sake of simplicity only the equalizer system for the left hand swell cylinder lever 38 and anvil plate 66 will be described in detail.

The equalizer system is composed of movable pairs of parallel elements. The first element is the boom 18 with its inner end pivotally connected to the shuttle carriage 24 which forms the second element of the system and is vertically fixed relative to the boom. The third element consists of a system of cables extending along the top of the boom 18 to the swell cylinder lever 38. The first cable 26 is connected at its inner end to the top of the shuttle carriage 24 and at its outer end to a pivoted bell crank arrangement 27 spaced from the outer end of the boom 18. The bell crank 27 allows the cable system to change direction without affecting the geometrical relationship of the equalizer system. A second cable 28 extends from the bell crank 27 to the upper end of the swell cylinder lever 38 forming the fourth element of the equalizer system and on which is mounted the anvil plate 66.

Since the first and third elements, the boom 18 and the cable system 26, 27, and 28, move in a substantially parallel relationship relative to one another and the second element, the shuttle carriage 24, is vertically fixed relative to the remainder of the system, the fourth element, the swell cylinder lever 38 must remain parallel to the fixed vertical carriage 24 and vertically oriented regardless of the angular position of the boom 18.

The ladder 17 is tilted from side to side of the hold 13 relative to the perpendicular around the pivot wheels 47 and 48 by a pair of substantially horizontal hydraulically actuated tilt cylinders 847 only one of which is visible in FIGURE l, extending between the boom 18 and the top of the ladder 17. The inner end of the tilt cylinder 84 is pivotally connected to approximately the second panel point on the boom 18 by a ball and socket joint 86 and the outer end is pivotally connected to an A-frame structure 90 on the top of the ladder 17 about the ladders pivot point by another ball and socket joint 88.

.FIGURE 5 is a schematic representation of the hydraulic system for the swell cylinders 31 and 32. To increase the volume of fiuid `within the cylinders as the pistons move upwardly, the swell cylinders 31 and 32 are connected by a main hydraulic line 92 to a pump 93 through a check valve 94. To assure the quick response of the system to sudden increases in volume caused by the upward movement of the swell cylinder pistons, a hydraulic accumulator 96 maintains a substantially constant pressure on the system. A pressure release valve 97 is provided in the main line 92 to release any excessive pressure build-ups in the system, and a two-way solenoid operated spring return pressure bleed off valve 98 is also provided through which the operator selectively vents the system to lower the pistons within the swell cylinder.

The swell cylinders 31 and 32 are provided with sets of limit switches 99 and 10()` respectively each set consisting of three position responsive limit switches a, b, and c. The upper switch a turns on an indicator when the episton is in its uppermost position within the swell cylinder. The lowermost switch c functions both to indi cate when the piston is at its lowermost position and to turn on the pump 93 to increase the volume of fiuid within the pressurized system. And, the intermediate switch b turns off the pump 93 when the piston reaches a predetermined intermediate position within the swell cylinder.

Since the entire ladder structure pivots about the pivot wheels 47 and 48 lwhich are offset inshore of the centerline of the ladder structure 17, the entire ladder structure 17 is subjected to an unbalancing force tending to move the excavating wheel 15 in the inshore direction. This inshore force is resisted by both the pivot wheels 47 and 48 bearing against the vertical anvil plates 65 and 66 on the boom 118 and the restraining force exerted by the tilt cylinders 84 on the top of the ladder structure.

The operator initially begins the operation of the apparatus by introducing fluid into the swell cylinders to raise the ladder structure toward the uppermost position. As the excavating wheel 15 and the elevator 20l till up, the entire ladder structure 17 gradually overhauls the accumulator pressure and sinks toward a normal working position in which the swell cylinder pistons are near the bottom of the piston stroke. Once the normal working position is achieved, the live load of the ladder structure is effectively counterbalanced by the pressure in the swell cylinder system and the ladder structure 117 is in effect oating relative to the boom 18. Therefore, when the ladder structure is subjected to any substantial vertical component of force, as by an unusual drop in either the boom hoist motion, an upsurge of the tank top 102 caused by a harbor swell, or a collision of the wheel with any object, the ladder structure will move upwardly to release the forces. As the ladder structure 17 moves vertically relative to the boom 18, the pivot wheels 47 and 48 merely roll up or down the anvil plates 65 and 66.

The suspension system 30 of the present invention accommodates not only vertical motion of the ladder structure 17 relative to the boom 18 but also a conical pendulous motion of the ladder structure within the hold 13. The pendulous motion is approximately 6 in the fore and aft direction and 5 from side to side of the perpendicular within the hold I,13.

Side to side pendulous movement of the ladder structure is produced by actuating the horizontal tilt cylinders 84 to pivot the ladder structure 17 about the pivot wheels 47 and 48 on either side of the perpendicular. This motion is of substantial benefit because it extends the reach of the excavating Wheel 15 under the hatch coarnings 101 of the hold 13 and reduces the amount of material which must be removed by the slower final clean-up methods.

[Fore and aft pendulous motion of the ladder structure 17 is made possible by the combination of the two spaced vertical swell cylinders 31 and 32 and the pivot wheels 47 and 48. Since the swell cylinder piston rods are pivoted to the cross shaft by ball and socket joints andthe pistons are not bottomed within the swell cylinders under normal working conditions, the pistons are free to move differentially with the swell cylinders whenever the ladder structure 17 is subjected to a force in either the fore or aft direction. Thus, either fore or aft 4forces on the ladder structure 17 cause one swell cylinder piston to move upwardly and the other downwardly as the lower end of the piston rods swivel about their ball and socket connections and the pivot wheels 47 and 48 roll or slide across the faces of the anvil plates 65 and 66.

IWhile the preferred embodiment of the invention has been described in considerable detail, it is to be understood that many rearrangements and modifications may be resorted to without departing from the scope of the invention as defined in the following claims.

What is claimed is:

`1. In material handling apparatus including support means, boom means mounted on said support means, carrier means attached to said boom means, excavating means mounted on said carrier means and means suspending said carrier means from said boom. means the improvement comprising said suspending means including pressurized piston and cylinder means interconnecting said boom means and said-carrier means and being so constructed and arranged that the pressure within said piston and cylinder means counterbalances substantially all of the vertical working load of said carrier means and said excavating means, and means to change the volume of fluid within said piston and cylinder means responsive to the Working load on said carrier and excavating means, and thereby maintain a substantially constant pressure therein whereby said carrier rises and falls relative to said boom with sudden changes in load.

2. A device as set forth in claim '1 wherein said volume increasing means includes |pump means connected to said piston and cylinder means.

3. A device as set forth in claim 1 wherein said volurne increasing means includes hydraulic accumulator means.

4. A device as setforth in claim :1 wherein said suspending means includes a ball and socket connection between said piston and cylinder means and said carrier means.

S. A device as set forth in claim 1 wherein said carrier means pivots relative to said boom about a point and said suspending means includes cooperating pivot wheel and anvil means so constructed and arranged that as said carrier means moves relative to said boom means said pivot wheel and anvil means roll relative -to one another to allow the pivot point of said carrier ymeans to move relative to the boom means.

6. A device as set forth in claim 5 wherein said pivot point is offset relative to the center line of said carrier means, and restraining means are provided toflimit rotation of said carrier means about said pivot point.

7. A device as set forth in claim 6 wherein said restraining means includes piston and cylinder means operative to tilt said carrier means relative to said boom means about said pivot point.

8. Bulk material handling apparatus comprising support means, boom means mounted on said support means, ladder means suspended from said boom means, excavating means carried by said ladder means, suspension means interconnecting said boom means and said ladder means including substantially vertically disposed first liuid actuated piston and cylinder means, said iirst piston and cylinder means being connected at its opposite ends to said boom means and said ladder means, anvil plate means on said boom means, and pivot wheel means rotatably mounted on said ladder means adjacent one edge thereof and in engagement with said anvil plate means, pivoting means extending between said boom means and said ladder means and engaging said ladder means at a point vertically spaced from said pivot wheel means, and means to charge the volume of fluid within said first piston and cylinder means thereby maintaining a substantially constant pressure therein to counterbalance the working load of said ladder means and said excavating means.

9. A device as set forth in claim 8 wherein said pivoting means includes second piston and cylinder means adapted to be selectively actuated to either restrain movement of said ladder means or to pivot said ladder means on either side of a perpendicular position.

10. A device as set forth in claim 8 wherein said suspension means includes substantially vertical lever means having said anvil means thereon and being pivoted adjacent its lower end to said boom means, said first piston and cylinder means being connected at one end to the upper portion of said lever means.

11. A device as set forth in claim 10 wherein equalizer means are provided on said boom means for maintaining said lever means in a vertical position regardless of the boom angle.

12. A device as set forth in claim 11 wherein said equalizer means comprises cables extending from the top of said lever means along said boom means to a fixed vertical member on said support means.

13. A device as set forth in claim 8 wherein said excavating means comprises a rotary digging wheel.

References Cited UNITED STATES PATENTS 2,365,818 12/1944 Herrick et al 214-14 XR 2,757,376 7/ 1956 Brueder 267-65 XR 2,796,180 6/1957 Rose 214-14 2,956,796 10/ 1960 Devillers 267-65 3,062,392 11/ 1962 Eppard 214--14 3,091,874 6/1963 Wuigk 37--190 ROBERT E. PULFREY, Primary Examiner. CLIFFORD D. CROWDER, Assistant Examiner. 

